Similar to many ebay users I buy older phones on ebay and flash a different system ROM to the devices to get an up to date version of Android with regular security updates (devices that no longer receive updates from the OEM).
I'm using the Android 15 based LineageOS 22.2, with latest updates and can no longer install the ebay app on my phone.
I can only assume that the latest app update also requires working Google play "Safety Net", which only works on official Android releases, not just an Android 10+ version.
Ebay appear to have joined the somewhat arbitrary list of companies which require safety net. (The Disney+ app works on my phone but I can't install Netflix. Some banking apps work, some don't. *shrugs*)
Tried installing the web site to my home screen but it seems all link targets in the page are shifted away from the actual link text. You have to click on the menu item above to hit the one you want. Works ok in browser though. So we can't even have ebay as a functional PWA on mobile.
ebay have just made it harder for me to by a used phone from ebay...on my used phone from ebay.